int create_subcgroup(pid_t pid, bool keep_unit, CGroupUnified unified_requested) {
_cleanup_free_ char *cgroup = NULL;
CGroupMask supported;
const char *payload;
int r;
assert(pid > 1);
/* In the unified hierarchy inner nodes may only contain subgroups, but not processes. Hence, if we running in
* the unified hierarchy and the container does the same, and we did not create a scope unit for the container
* move us and the container into two separate subcgroups.
*
* Moreover, container payloads such as systemd try to manage the cgroup they run in in full (i.e. including
* its attributes), while the host systemd will only delegate cgroups for children of the cgroup created for a
* delegation unit, instead of the cgroup itself. This means, if we'd pass on the cgroup allocated from the
* host systemd directly to the payload, the host and payload systemd might fight for the cgroup
* attributes. Hence, let's insert an intermediary cgroup to cover that case too.
*
* Note that we only bother with the main hierarchy here, not with any secondary ones. On the unified setup
* that's fine because there's only one hiearchy anyway and controllers are enabled directly on it. On the
* legacy setup, this is fine too, since delegation of controllers is generally not safe there, hence we won't
* do it. */
r = cg_mask_supported(&supported);
if (r < 0)
return log_error_errno(r, "Failed to determine supported controllers: %m");
if (keep_unit)
r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 0, &cgroup);
else
r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, pid, &cgroup);
if (r < 0)
return log_error_errno(r, "Failed to get our control group: %m");
payload = strjoina(cgroup, "/payload");
r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, payload, pid);
if (r < 0)
return log_error_errno(r, "Failed to create %s subcgroup: %m", payload);
if (keep_unit) {
const char *supervisor;
supervisor = strjoina(cgroup, "/supervisor");
r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, supervisor, 0);
if (r < 0)
return log_error_errno(r, "Failed to create %s subcgroup: %m", supervisor);
}
/* Try to enable as many controllers as possible for the new payload. */
(void) cg_enable_everywhere(supported, supported, cgroup);
return 0;
}
int create_subcgroup(pid_t pid, CGroupUnified unified_requested) {
_cleanup_free_ char *cgroup = NULL;
const char *child;
int unified, r;
CGroupMask supported;
/* In the unified hierarchy inner nodes may only contain
* subgroups, but not processes. Hence, if we running in the
* unified hierarchy and the container does the same, and we
* did not create a scope unit for the container move us and
* the container into two separate subcgroups. */
if (unified_requested == CGROUP_UNIFIED_NONE)
return 0;
unified = cg_unified(SYSTEMD_CGROUP_CONTROLLER);
if (unified < 0)
return log_error_errno(unified, "Failed to determine whether the unified hierarchy is used: %m");
if (unified == 0)
return 0;
r = cg_mask_supported(&supported);
if (r < 0)
return log_error_errno(r, "Failed to determine supported controllers: %m");
r = cg_pid_get_path(SYSTEMD_CGROUP_CONTROLLER, 0, &cgroup);
if (r < 0)
return log_error_errno(r, "Failed to get our control group: %m");
child = strjoina(cgroup, "/payload");
r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, child, pid);
if (r < 0)
return log_error_errno(r, "Failed to create %s subcgroup: %m", child);
child = strjoina(cgroup, "/supervisor");
r = cg_create_and_attach(SYSTEMD_CGROUP_CONTROLLER, child, 0);
if (r < 0)
return log_error_errno(r, "Failed to create %s subcgroup: %m", child);
/* Try to enable as many controllers as possible for the new payload. */
(void) cg_enable_everywhere(supported, supported, cgroup);
return 0;
}
